The effect of 30% N2O on the general hemodynamics of patients with heart valve lesions

The effect of 50% N2O on the general haemodynamics of patients with heart valve lesions was evaluated. The addition of N2O to oxygen before cardiopulmonary bypass was associated with a decrease in the cardiac output from 3.60 +/- 0.23 to 3.04 +/- 0.17 l.min-1/m2 (P less than 0.001) although the filling pressure of the left ventricle remained constant and right ventricle preload was increased from 8.18 +/- 0.99 to 9.85 +/- 1.14 mmHg (P less than 0.05). Because the systemic blood pressure fell after N2O was added, the decrease in cardiac output is interpreted as representing a decrease in myocardial contractility. The changes in the inverse relationship between arterial blood pressure and stroke volume also support the concept that N2O suppresses myocardial contractility.